It is known generally to provide vibration alert sensations in cellular telephones by rotating an eccentrically mounted mass. These rotary devices however have slow response and attack times, which substantially limits their range of applicability. Rotary vibration devices are used primarily for alerting users to incoming calls or messages, an application for which expedient response times are not required.
U.S. Pat. No. 5,528,697 entitled “Integrated Vibrating And Sound Producing Device” discloses an integral device capable of producing both audible buzzer sounds and/or low frequency vibrations for use in radio-activated paging devices and in signal receivers for hearing-impaired individuals.
Integrated multi-function transducers inevitably compromise performance of both vibration and audio functions. Dynamic loudspeakers, for example, are preferably mounted in cavities having a closed-end portion and an open-end to promote optimal sound propagation. Mounting integrated devices in cavities, however, tends to compromise the vibrator performance.
Existing integrated multi-function transducers suitable for use in cellular telephone applications also have large dimensions, since minimal transducer thickness and minimal diameter are required to provide user perceptible vibration signal amplitudes and sound pressures. In at least some applications, particularly in increasingly smaller cellular handsets favored recently by consumers, large integrated transducer packages pose substantial integration and assembly issues. Additionally, potential radio frequency interference between integrated transducers and radio antennas limits where integrated transducers may be mounted in handset housings.
The various aspects, features and advantages of the present inventions will become more fully apparent to those having ordinary skill in the arts upon careful consideration of the following Detailed Description of the Invention with the accompanying drawings described below.